Colloidal silica has many known industrial uses including frictionizing agents for textiles, improvement of polymeric materials including lowering Coefficient of Thermal Expansion, raising of Young's Modulus and Tensile strength, lowering % Elongation, raising electrical insulating properties and resistance to electrical breakdown voltage, production of more efficient catalyst materials, and many other useful functions. Colloidal silica can be used in its original aqueous form or be converted to nonaqueous colloidal dispersions for use in applications that do not tolerate the presence of water.
It is known to be advantageous to attach organic surface character to the surface of colloidal silica particles of aqueous solution. One such application is latex and emulsion polymerization chemistry, where the addition of surface-treated colloidal silica can improve and modify the physical properties of the dried or cured latex coating. The addition of organic surface character to latex coatings can impart stability and shelf life to the colloidal silica component of a latex coating formulation.
U.S. Pat. No. 7,544,726 “Colloidal Silica Compositions”, issued 9 Jun. 2009, describes and claims a method of producing a stable aqueous silanized colloidal silica dispersion without the presence of any water-miscible organic solvents or optionally comprising one or more water-miscible organic solvents, if present, in a total amount of up to about 5% by volume of the total volume, said dispersion having a silica content of at least 20 wt %, said method comprising mixing at least one silane compound and colloidal silica particles in an aqueous silica sol having an S-value from 30 to 90 in a weight ratio of silane to silica from 0.003 to 0.2. It also describes and claims a stable aqueous silanized colloidal silica dispersion without the presence of any water-miscible organic solvents or optionally comprising one or more water-miscible organic solvents, if present, in a total amount of up to about 5% by volume of the total volume, said dispersion having a silica content of at least 20 wt % obtained by mixing colloidal silica particles and at least one silane compound in an aqueous silica sol having an S-value from 30 to 90 in a weight ratio of silane to silica from 0.003 to 0.2. It also describes and claims a stable aqueous silanized colloidal silica dispersion without the presence of any water-miscible organic solvents or optionally comprising one or more water-miscible organic solvents, if present, in a total amount of up to about 5% by volume of the total volume, said dispersion having a silica content of at least 20 wt % and having a weight ratio of silane to silica from 0.003 to 0.2, wherein colloidal silica particles are dispersed in a silica sol having an S-value from 30 to 90.
U.S. Pat. No. 7,553,888 “Aqueous Dispersion”, issued 30 Jun. 2009, describes and claims a method of producing an aqueous dispersion comprising mixing at least one silane compound and colloidal silica particles to form silanized colloidal silica particles and mixing said silanized colloidal silica particles with an organic binder to form the dispersion. The invention also relates to a dispersion obtainable by the method, and the use thereof.
U.S. Pat. No. 5,013,585A, “Method for the Preparation of Surface-Modified Silica Particles” (issued 7 May 1991 and expired 6 Jun. 2010), describes and claims a method for the preparation of a stable silica organosol in a monomeric hydrophobic organic solvent. The method comprises (a) hydrolyzing a tetraalkoxy silane, e.g. tetraethoxy silane, in an alcoholic medium in the presence of a limited amount of water and ammonia as a catalyst under controlled conditions so as to produce a silica alcosol in which the silica particles satisfy the requirements that the alkoxy groups and silanolic hydroxy groups are bonded to the silicon atoms on the surface in densities of at least 3.5 μmoles/m2 and not exceeding 2 μmmoles/m2, respectively, and the specific surface area S given in m2/g and the average particle diameter D given in nm of the silica particles satisfy the relationship of S×D≥5000, D being 1 nm or larger, and (b) admixing the alcosol of silica particles with an organosilicon compound selected from the group consisting of the compounds represented by the general formula R4-nSiXn, (R3Si)2NH, or YO—(—SiR2—O—)m—Y, in which each R is, independently from the others, a hydrogen atom or a monovalent hydrocarbon group, X is a hydroxy group or an alkoxy group, Y is a hydrogen atom or an alkyl group, n is 1, 2 or 3 and m is a positive integer not exceeding 20, in an amount, for example, in the range from 0.01 to 10 moles per mole of the silica particles under agitation of the mixture to effect a reaction for the modification of the surface of the silica particles followed by replacement of the alcoholic medium with a desired organic solvent.
The article “Functionalization of Colloidal Silica and Silica Surfaces via Silylation Reactions” by J. W. Goodwin, R. S. Harbron and P. A. Reynolds was published in Colloid and Polymer Science. August 1990, Volume 268, Issue 8. pp 766-777. The word described in this article relates to a series of trialkoxysilane compounds tipped with primary amine groups being used to functionalize the surfaces of glass and colloidal silica. Streaming potential and microelectrophoretic mobility measurements were used to monitor the stability of the functionalized surfaces. Hydrolytic breakdown of the surface-to-silane coupling was induced by either successively increasing and decreasing the pH of the solution in contact with the surface, or by aging the derivatised surfaces in aqueous solution over prolonged periods of time. The chemistry of the spacer units between the trialkoxysilane group and the primary amine tip had a major influence on the subsequent hydrolytic stability. Large monomeric hydrophobic spacer groups showed small changes in the electrokinetic properties on storage, but large changes when successively titrated with acid and base through the pH range. The behavior observed with small monomeric hydrophobic spacer groups was that large changes in electrokinetic properties were obtained on storage and with pH titration.
The article “Use of (Glycidoxypropyl)trimethoxysilane as a Binder in Colloidal Silica Coatings”, by L. Chu, M. W. Daniels, and L. F. Francis, was published in Chem. Mater., 1997, 9 (11), pp 2577-2582. In this work, colloidal silica coatings were produced from suspensions of silica modified with (glycidoxypropyl)trimethoxysilane (GPS). Coating dispersions were prepared by adding GPS to a silica colloid (12 nm) suspension. Adsorption of hydrolyzed GPS species on silica surfaces was monitored by attenuated total reflection Fourier transform infrared spectroscopy. The addition of GPS to a basic silica suspension (pH 9.5) favored condensation among hydrolyzed GPS species over adsorption. By contrast, more adsorption on the silica colloids occurred in acidic suspensions (pH 4) and condensation among hydrolyzed GPS species was slower. The interaction between GPS and colloidal silica was also reflected in the aggregation and gelation behavior of the suspensions and the coating microstructure. Suspensions prepared by addition of GPS at low pH resulted in coatings that were less prone to cracking. In addition, polyamine could be added to these suspensions to cure the coatings. Compared with unmodified silica coatings, coatings prepared with GPS modification were denser, adhered better to the polymer substrate, and could be made thicker (up to 20 μm). Coatings were also transparent to the eye.
Colloidal silica can be used in treatment fluids for enhanced oil recovery, specifically in downhole injection treatments to hydrocarbon-bearing subterranean formations for improving oil recovery in downhole applications such as fracturing, stimulation, completion, and remediation.
Commercially available colloidal silica mixtures suitable for these treatment fluids include the nanoActiv™ HRT product line available from Nissan Chemical America, http://www.nanoactiv.com/. These products use nanosized particles in a colloidal dispersion, which allows the fluid to work by causing a Brownian-motion, diffusion-driven mechanism known as disjoining pressure to produce long efficacy in the recovery of hydrocarbons in conventional and unconventional reservoirs.
US published patent application US2012/0168165A1 (abandoned 17 Dec. 2012), “METHOD FOR INTERVENTION OPERATIONS IN SUBSURFACE HYDROCARBON FORMATIONS” describes and claims colloidal silica added to a fluid containing a wetting agent to enhance wetting of solid surfaces in and around the well and removing a water-block from the well. The wetting agent and colloidal silica combine to produce a wetting of the surfaces of the rock that allows recovery of the excess water near the well (water block).
US published patent application US2012/0175120 (abandoned 29 Nov. 2012), “METHOD FOR INTERVENTION OPERATIONS IN SUBSURFACE HYDROCARBON FORMATIONS”, describes and claims colloidal silica added to a fluid containing a wetting agent and the fluid is pumped down a well to enhance wetting of solid surfaces in and around the well before pumping an acid solution down the well. After acid is pumped, a fluid containing colloidal silica and wetting agent is again pumped down the well, leading to improved flow capacity of the well.
US published patent application US2010/096139A1 (abandoned 9 Oct. 2012) “METHOD FOR INTERVENTION OPERATIONS IN SUBSURFACE HYDROCARBON FORMATIONS”, describes and claim methods for improved intervention processes in a well. Colloidal silica is added to a fluid containing a wetting agent to enhance wetting of solid surfaces in and around the well, leading to improved flow capacity of the well.
US published patent application US 2016/0017204, “METHODS AND COMPOSITIONS COMPRISING PARTICLES FOR USE IN OIL AND/OR GAS WELLS”, now pending, describes a method for treating an oil and/or gas well comprising combining a first fluid and a second fluid to form an emulsion or microemulsion, wherein the first fluid comprises a plurality of monomeric hydrophobic nanoparticles and a non-aqueous phase, wherein the second fluid comprises a surfactant and an aqueous phase, and wherein in the microemulsion, a portion of the nanoparticles are each at least partially surrounded by surfactant and in contact with at least a portion of the non-aqueous phase; and injecting the emulsion or microemulsion into an oil and/or gas well comprising a wellbore.
These patent applications discuss the use of a mixture of colloidal silica in combination with a wetting agent for modifying solid rock surfaces in an aqueous or hydrocarbon-based fluid for injection into an oil well to effect improved oil recovery. They do not discuss the brine resistance properties of the colloidal silica.
It is generally well known in oilfield applications that subterranean formations contain large amounts of water containing dissolved salts such as NaCl, CaCl2, KCl, MgCl2 and others. This aqueous salt mixture is typically referred to as Brine. Brine conditions for different regions and wells vary widely with different downhole conditions and lithologies. In general, fluids used downhole must either tolerate briny conditions or have brine-resistant properties.
While these patent applications explore the use of colloidal silica, including aqueous colloidal silica, in downhole oilfield applications and there are commercial products containing colloidal silica available; none of these patent applications or commercial products address the utility of brine resistant colloidal silica.